​​Table of Contents
  1. What is a wormhole?
  2. A History of Wormholes
  3. Black Holes and White Holes
  4. Is it possible to travel through a wormhole?
  5. Traveling Through Time
  6. Intra- and Inter-Universe Wormholes
  7. Lorentzian Wormholes
  8. Euclidean Wormholes

What is a wormhole?
Wormholes Bend Space
Wormholes Bend Space

I'm glad you asked! A wormhole is a black hole and a white hole joined by a "throat", or tunnel. A wormhole can theoretically connect two points in space-time by warping space time, meaning time travel is theoretically possible!
Warping Spacetime
Warping Spacetime

A History of Wormholes
The term "wormhole" was created in 1957 by American physicist John Archibald Wheeler. However, mathematician Georg Riemann was the first person to formulate wormholes. He referred to them as "Riemann cuts" and claimed they connected spaces without​
Riemann Cut
Riemann Cut
any tunnels, contrary to popular modern belief. Einstein considered wormholes in his theory of special relativity. He worked with colleague Nathan Rosen, and the two believed that there was a worm hole at the center of every black hole that connected to a parallel universe. They called their wormholes Einstein-Rosen bridges. People disregarded their theory because matter cannot survive in a black hole; the only way through would be to travel at the speed of light, which was impossible. Roy Kerr found in 1963 that the collapsing star that created a black hole would not create a point at the end of the hole; it would create a ring that would allow access into a parallel universe. Wormholes were associated with time travel in 1985 when Kip Thorne theorized that a wormhole needed negative matter to remain open long enough for people to travel through. More recently, Stephen Hawking introduced the idea of an infinite amount of parallel universes, all connected by wormholes. Hawking along with Sidney
Einstein-Rosen Bridge
Einstein-Rosen Bridge
Coleman, a physics professor at Harvard who was prominent in the 1970s, both believed that there was an infinite number of small wormholes in the universe and that large wormholes would ultimately cause the universe to be unstable and explode.

More simplistically, in the mid-1800s, a man by the name of Charles Dodgson (under the pen name Lewis Carroll) wrote a book entitled Alice in Wonderland. As you probably know, Alice enters a rabbit hole and finds herself in an alternate world. In this world, the laws of physics were changed, allowing for extremely odd occurances. Sound familiar? Carroll actually wrote Alice in Wonderland to discuss the idea of parallel universes! In present day, the rabbit hole is compared to an Einstein-Rosen bridge. Carroll lived too early in history to know exactly how his imaginative idea was possible and had never heard of the term "wormhole," but many of the core concepts in Alice in Wonderland mimic the behavior of these portals through space-time.
Black Holes and White Holes
Black holes (click here for a cool interactive website) are areas of immensly strong gravity that overcomes all other forces. Not even light
Supernova Forming Black Hole
Supernova Forming Black Hole
can escape a black hole. According to Einstein's theory of relativity, gravity has the ability to bend light and therefore can stop it from leaving black holes. Here's how they're formed! Basically, when the core of a large star (probably at least twenty times bigger than our sun) collapses, a supernova explosion occurs. The star's mass continues to be compressed into a smaller and smaller amount of space until the black hole forms. The star's mass is held in the "event horizon" of the black hole, which is the boundary or opening where light can't escape. Many scientists believe black holes are at the center of many if not all galaxies, including our Milky Way.

White Hole
White holes are just the opposite- instead of swallowing everything up, they spit everything out. They also run backwards in time from black holes. However, these violate the Second Law of Thermodynamics. What does this mean? The law states that order can become disorder, but not the other way around. For example, you can break a glass, but the glass cannot be magically fixed. According to theories, white holes eject things that would have been destroyed by black holes...which is physically impossible. It would be like smashing the glass into a trashcan and the trashcan spitting out a perfectly whole glass. This doesn't necessarily disprove white holes though- the physics we observe on earth can be very different from the physics of the universe. Keep in mind, however, white holes are purely theoretical. They were devised because of mathematic equations, and many scientists believe that they cannot exist in nature. One reason for scientist's skepticism towards white holes is the fact that they disappear whenever they come in contact with matter. Therefore, even if white holes existed at the beginning of our universe, many scientists reason that they have all disappeared by now.

Is it possible to travel through a wormhole?
Travelling Through Wormholes
Travelling Through Wormholes

Scientists classify wormholes that things can travel through as transversable. The tunnel created by the black hole and white hole would have to stay open long enough for the object to pass through without being crushed by the black hole. For this to happen, the wormhole would have to remain unchanging in time and space. It would have to contain negative matter, also called "exotic" matter by some scientists because it is so different from any kind of matter we are familiar with.

Traveling Through Time
Theoretically, it is possible to travel through time as you are traveling through a wormhole. Since a wormhole connects two different universes or two different space times, you can travel through one and end up in another time. You would, of course, have to be traveling at the speed of light for this to occur. Traveling at this rate would make the trip through the time hole seem like no time to you, but numerous years to other. If you then traveled back through the hole, you would come back to the previous time. If you are going the speed of light, it would be as if you were never gone since you are traveling so fast through the time. This video shows a demonstration of this concept:

This video shows a teacher's demonstration of time travel through a wormhole!

Still confused? This video provides an excellent explanation and visual on what exactly travelling through space-time via a wormhole is all about:

Intra- and Inter-Universe Wormholes There are two main types of wormholes that are believed to exist. One is an intra-universe wormhole. This wormhole connects two places that are in the same universe. On the other hand, inter-universe wormholes connect two places that are in two different universes. Inter-universe wormholes theoretically allow for travel between alter universes. Check out this website for a simple explanation of white holes and wormholes!

Instability of Lorentzian Wormholes
Instability of Lorentzian Wormholes
Lorentzian Wormholes

Also called Schwarzschild wormholes, these kind of wormholes have not yet been disproven, although scientists have been studying them for about a decade. They are simply the joining of a black hole and a white hole by a throat, so they're the same concept as the Einstein-Rosen bridges. However, they are not transversable as far as scientists know, although Kip Thorne theorized they could be held open with a lot of negative matter (these transversable Lorentzian wormholes can be called Morris-Thorne wormholes, as Thorne developed the idea with student Mike Morris). The negative matter in coordination with the positive matter would create pressure that would keep the wormhole open. Unfortunately, it would be technologically impossible at this time for scientists to create enough negative matter to keep this kind of wormhole open long enough for travel. And this kind of wormhole requires a white hole, which violates the Second Law of Thermodynamics. Furthermore, these wormholes are incredibly unstable; there is so much gravity that it causes the wormhole to constatntly stretch, so the tunnel becomes longer but thinner. This would disable anyone from passing through the wormhole.

Check out this video on wormholes!
Theoretical Picture of a Wormhole
Theoretical Picture of a Wormhole

Euclidean Wormholes
Euclidean wormholes are much more complicated than Lorentzian wormholes. Euclidean wormholes are difficult to understand because they exist in "imaginary" time, a time unlike anything experienced on Earth. Being strictly virtual, these wormholes are studied by primarily quantum field theorists.

Ghost Radiation
Euclidean Wormhole
Euclidean Wormhole

Scientists have been studying a negative energy field called ghost radiation that could allow people to travel through wormholes. It would balance out the positive energy of matter and stabilize the wormhole long enough to allow for travel. However, it would be very hard to get the right balance of negative energy. If too much negative energy is added to the wormhole, it will explode into a universe that would expand rapidly at the speed of light (many scientists think this is what happened to our universe after the Big Bang). Research on ghost radiation is being conducted at Cern, where scientists are studying very small black holes that form from colliding particles; in the future, they hope to be able to test wormhole theories through the use of these black holes by attempting to send particles through them. But for now, ghost radiation seems to be rather far-fetched, as it would take negative energy equivalent to the mass of Jupiter to keep a wormhole open long enough for travel.

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*Wormhole Demonstration Video uploaded to YouTube by **docbobo2002**
*Wormholes Video uploaded to YouTube by **KurdstanPlanetarium** on February 3, 2009
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